Grid circuits of electron tubes



May 29, 1928.

S. P. SHACKLETON GRID CIRCITS OF ELECTRON TUBES Filed May 16, 1923 2 Sheets-Sheet 1 INVEN TOR 61 I? Skadi/fam A TTORNEY May 29, 1928. 1,671,130

S. P. SHACKLETON GRID CIRCUITS OF ELECTRON TUBES y Filed May 16, 1923 2 Sheets-Sheet 2 2 I X (l 2.3' f I ll 'v mim) N 24 E n 25 ?4\\ 2y Il E@ 2f 29 25`\ l /2-9' I S E f E v 2445115) 45mg m Amwwm 10 49 Y 27 X M '27 M' /29' E E@ "i 2 HM) 1(0) 1 E 'vot z :v uw, /a la if ATTORNEY Patented May 29, 192.8.

UNITEDv STATES PATENT "OFFICE- i,

SAMUEL I. SI-IACKLETON, OF WYOMING, NEW JERSEY, ASSIGNOR TO AMERICAN TELE- Y' PHONE AND TELEGRAPH COMPANY, A CORPORATION 07F NEW YORK.

GRID CIRCUITS OLE* ELECTRO`N` TUBES.

Application sied yMay 16,

This intention relates` to improvements in circuits for impressing potentials upon the grids of electron tubes and is particularly adaptable for use with electron tubes em ployed in telephone repeater circuits.

When electron tubes are used as amplifying elements in telephone repeaters the grid of each tube is usually .maintained at negative potential with respect 'to the filament. A desirable potential difference between grid and filament has been found in many instances to be approXimatelyQ volts. In some instances the negative potential on the'grid has been obtained by a small battery connected in the input circuit ofthe tube, a separate battery being used for each grid. In arrangen'ients more recently developed the individual grid battery was done away with and the grids-of all the repeater tubes of an installation were excited from a common battery. Such an arrangement is il lustrated in the U. S. Patent-No. 1,385,777 to A. B. Clark. In other arrangements the potential difference between ther grids and' filaments was provided for by circuits utilizing the potential drop in the filament 'circuit itself. In these last mentioned types of systems, namely those utilizing a common grid or C battery or those utilizing the potential drop inthe filament circuit, it has been found t-hat wider voltage variationsy may exist in the potential difference between grid and filament than are desirable. It is accordingly the general object of this inveiition to provide arrangements whereby the voltage variations in the desired potential difference between the grids and filaments will be reduced to amaterial degree and the operation of the tubes greatly im.

proved. Other objects and features of the invention will appear more fully from the detailed description hereinafter given.

The invention may be more fully under-l stood from the following description to gether with the accompanying drawing in the Figures 1, 2, 3 and 4 of which the inven ti-on is illust-rated. In Fig. 1 are shown arrangements of the prior art andv their disadvantages. In Figs. 2, 3 and 4 are shown circuit diagrams embodying this invention.

In Fig. 1 is shown an arrangement of the prior artin which a common C battery is provided for supplying potential to the grids. Such an arrangement is shown in detail in the aforementioned Patent No. 1,385,-

i923.` yserial No. 639,419.

777 to A. B. Clark and reference maybe had thereto for circuit details not illustrated Y therein. Four electron tubes D, E, F and G are shown having their filaments connected in series.

The filament circuit may bev traced as follows: from the `negative terminal ofbattery A, through inductance lO and resistance 11, through the filaments at tubes Cr, F, E and D inv series, to the positive terminal of battery A. Resistance 11 is variable sov that the filament current may be heldy constant and the coil 10 is highly inductive and thus prevents the disturbances on bat-A tery A from being transmitted to the talking circuits. Connected to points `of difai'e conductors leading to the grids ofv each n to, ferent potential on the common C battery l y tube.r For reasons which will be apparent it kshould here be noted that because of the series connection of the filaments the filament potential decreases from tube to tube due tothe filament resistance, and if,.for n example, there is a 4.5.volt drop in each filamentthe lowest potential in the filamentsl of tubes D, E,Fand Gr wouldbe respectively -4.5, 9, flfv and ,-18 volts. As

a 9 volt differencevofpotential between each Grid and filament is desired they grids of.y

*22.5, and -27 volts. It has been found in practice, however, that the potential dropy due to theifilament resistance will not be exactly 4.5 volts but will varyv for -eachfila- `ment so that it must be'termed 4.52:.5volts. If wenow look at the seriesfilament circuit with this variation in the filament drop in tubes D, E, Fand Cr respectively are con-A nected to points on battery C of 135, #-18,v

mind it will be seen that. point 1 will have n zero potential the potential of point 2 will be (-4i.5)1volts, point 3' will be (-4i.5) volts, point 4 will be (-9i1) volts due tol the fact that the variation of both filaments will be cumulative,point 5 will be (-911) y 13.5i1.5) volts kdue to the fact that the variation ofthe threer volts, point 6' will be Vgrid and filament for tube D of (9th) volts,l a potential difference for tube AE of (9i1) volts, and a potential difference for tube F.

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`of all the tubes will be kept from varying beyond the limit of (9i 1) volts, thereby ensuring the proper operation of' all of th-e tubes. i

In Fig. 2 is shown `a circuit `diagram il` lustrating schematically the arrangements of the invention. Similar reference charac` ters have been used to denote like parts in both Figs. 1 and 2. Fourelectron tubes D,

F and G are shown with their filaments yconnected in series in the following circuit: fromb'attery A, inductance 10, resistance 11, through the Afila-ments of tubes G, F, E and D in series to battery A. yResistance 11 is variable, so `that the filament current may be held Iconstant and the coil 10 is highly inductive and thus prevents disturbances on battery A from being ltransmitted tothe ta-l'lcing circuits. `The voltages at points l, 2, 3, 4, 55, 6, 7 and f8, will be the same as heretofore pointed out with respectto Fig. 1 and are so marked on the drawing. A nine .volt diE-erence in potential between grids and filaments is desired. Accordingly the grid of "tube D isconnected. as shown `to point 6 which has a voltage of (-1345i1-5).

` The voltage difference accordingly between grid 'and filament Aof tube D will be within the :limits `of (.Ql) volts, for if' the voltage at point '2 is (-4.`5+.'5) the voltage of the grid will be v(-13.5l-1.5) .and if the voltage at poin't`2 Ais (-4,'5 --5) the voltage of the grid willbe `(*13.5-1.5). As has been pointed out with respect to Fig. 1, a voltage difference between grid `and filan'ient which `remains within the limits of t 9:*:1) volts will insure satisfactory operation of the tube.` The grid `of tube E is connectedas `shown to point 8 and accordingly will have a potential of (-18i2) volts. The voltage of the filament, as `will be seen from point 4, will be (-91-1) volts. Accordingly the voltage difference Vbetween grid and filament will be within .the limits of (V'Qil) volts, which will allow satisfactory operation of the tube. "The grid 'of tube F will be con* nected over Aconductor 12 and through the batte-ry "C1 to the point 14 of the filament circuit.` Point 14 will have the same potential as point 8 which is (-18i2) volts. The battery C1 in this instance will have a voltage drop of 4.5 volts, although in other instances its voltage drop might be different. Accordinglyvthe voltage of the grid of tube The voltage of' the filament, as will be seenfrom `point (i, will be 13.5i1-5). Accordingly the voltage difference between grid and filament of tube` F will be within the limits ofttlil) volts, which will allow satisfactory operation oil the tube. The grid of` tube G' will be connected over conductor `13 to battery C2 and thence through battery C1 to point 14. Battery C2 in this instance will have a voltage drop 0114.5 volts although in other instances its voltage drop might be different. Accordingly the grid of tube G ywill be [(-isim -t pas) -l-(-i.5)]`= (eerie). The voltage of' the filament as will be seen from point 8 is (-18222). Accordinglythe l voltage difference between grid and filament voltage of the i of tube G will be within the limits of ('Qil) p volts, which will allow satisfactory operation of the tube.` The invention. in other words combinetl the feat-ure ot' a common C or grid battery with that of utilizing the potential drop in` the filan'ient circuit itself so `that the .*oltage difference between the grid and filament of each tube will remain the desirable limits of (Sil) volts.

In Fig. 3 is shown an arrangement whereby a plurality ot' groups of tubes` may have their grids supplied with potential in accord yance wit-h this invention. Similar reference characters have beenused to denote like parts The apparatus shown in the drawing comprises two groups X and Y of tubes or amplifiers for f 'telephone circuits, each `group comprising with respect to the other figures.

four independent talking' circuits not shown in their entirety, but indicated merely by` Vinput transformers 22, 23, 24, 25 and 22',

23', 24", 25 and output transformers 26, 27, `28, 29 and 2G', 27', 28,29. The talking 'circuits are associated with the electron tubes D,`E, F, Gr and D, t', F, i. The arrange-l ments of the circuits are substantially the e same shown Iin Fig. 2. Each individual filament will Y L (4.5115) volts.` Tubes D, E, F and G `have their filaments connected in series as follows: from batt-ery A, through filaments of tubes D, E, F and G in series, conductor 20, resistance 11, inductance 10 to battery-A. Resistance 11 is variable so tha-t the filament cause a `voltage dron fof current may be held const-ant land coil 10 is highly inductive and thus prevents disturb-v anees on the battery A `from being-transmitted to the talking circuits. The pot-en-` tials of the filaments will be the same as heretofore pointed out with respect to Fig. 2 and are so indicated at points 2, 4, 6 and 8 of the drawing as t -4.5i.5), fit1), (-18.5i1-5) and -18i2) volts respectively. The grid of tube D is connected to point6 so that it will have a potential of- (-13.5i1.5) volts and so that the voltage differencev between grid and filament of the tube will be within the desired limits of (Qil) volts. rIhe grid of tube E isv connected to pointy 8 so that it will havepa potential of (-18i2) volts and so that the voltage 'difference between grid and filament of the tube will be within the desired limits of (9221) volts. The grid arrangements of tubes D and E, it will be seen, are the same as already described with respect to Fig. 2.

The grid of tube F will be connected over conductor 12, inductance 16, battery C1, conductor 15, resistance R', to point 14. Point 14 is connected by conductor 20 to point 8 and hence will have a potentialvof (-1812) volts. Battery C, Will have a voltage drop in this instance of 4.5 volts. Accordingly the voltage of vthe grid of tube F will be (-22.5i2) volts and the voltage difference between grid and filament of the tube will'.

. ingly the voltage ofthe grid of tube G will be (-27 i2) volts and the voltage difference between the grid and filament of the tube will be within the desirable limits of (9i 1) volts. The grid circuit arrangements of the tubes of set Y will be substantially the same as those heretofore described and no further description thereof will be given. The plate circuits of the tubes comprise the common B battery and the inductances and compensating resistances 16 and 16 and are substantially similar to the arrangements shown in the heretofore mentioned Patent 1,385,777 to A. B. Clark. As has been already pointed out the elements R and R are of higher resistance but as practically no current flow exists in the grid circuits these elements will cause no potential drop therein. It is desirable that the potential at points 14 and 14 should in the arrangements shown remain fixed at (-18i2) volts. If the resistances R and R were not included in the arrangements and if one of the tubes of group Y should burn out or become otherwise defective, current from` battery A would be supplied to point 14 through both coils 10 and 10 in parallel and thus tend to increase the voltage at point 14 beyond (-18i2) volts. However the values i of the resistances R and R are so great that they practically prevent any current flow bef of (-12i1) volts.

ltween points 14fand 14'overconductors15 and `15,s0 that anyA variation in the Y set. of tubes will cause no change in potential at point 14 and vice versa.y Additional` groups of tubes might have their grid po-I tentials supplied in a `similar manner from' battery A. Elimination of interference between the various talking circuits is taken care of by providing a low impedance alternating currentpath to ground from the grid batteries as illustrated by the coils 16 and 18 and condensers 17 and 19. y .Y In Fig. 4 is shown an alternative arrangement of the invention in Awhich different types of tubes areutilized,fsuch as tubes that Ihave a 6 volt drop due to filament resistance rather than a 4.5 yvolt drop. Similar reference characters have been utilized to denote like-parts `with respect to the other figures of the drawing. The apparatus shown comprises .two groups X and Y of tubes or *amplifiers for telephone circuits, each group comprising two independent talking` circuits not shown in their entirety but indicated merely by input transformers 27, 28, and 27', 28',

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and output transformers 29, 30, and 294,730. Thetalklng clrcuits are associated with electron tubes L, M and L, M. Thefilament circuits for tubes-L and M may betraced as follows: `from battery A, through the filaments of tubes L and M in series, conductor 20, resistance o and'resistan'ce 11, inductance f 10 to battery A. Point 1 of tube L will have a potential of zero. Due to the filament resistance point 2 of tube L will have a potential of (-6i-5) volts. Point 3 of tube M will have a potential of (-6if-5) volts. Point 4- of tubeM due to the filament re-y sistance; of both tubes-Will have a .potential The resistance 7- is designed to cause a drop in the voltage of 1 volt. Accordingly point 14 will have the voltage of point 4 plus the drop caused by resistance r or in other 4words a potential of (-13i1) volts. The grid of tube L will be connected'over conductor 12, coil 16, battery C1, conductor 15, resistance R, to point 14. Battery C, in this instance will have a voltage of 2 volts. Accordingly the voltage of the grid of tube L will be (-1811) +2 or in other words (-15i1) volts. The difference in potential between grid and filament of tube L will thus be within the desirable limits of (Qil) volts. The grid of tube M will be connected over conductor 13, coil 18, battery C2, battery C1, conductor 15, resistance R, to point 14. Battery C2 in this instance iifill have a voltage of 6 volts. Accordingly the voltage of the grid of tube M will be (-6) -l- (-2) -I- (-131) or in other words (-2111) volts. The difference in potential between grid and filament of tube M will thus be within the desirable limits of (9i1) volts. The circuits for the tubes CIK those already described.` In other respectsthe circuit arrangements of `ll`ifgr 4 are similar to those of Fig., Sand no' further description thereo'willl be given. i

While thejinyention has been disclosed isn p certain specific anangcinents which are deemed desirable, it is understood that it is capable of embodiment 1n many and widely varied forms without departing fromv the termined potential and means in said conspirit of the invention as defined bythe appended claims.

What is claimed is :v

l. A pluralityY of electron tubes, a circuit connecting the filaments of said.` tubes in series, conductors leadingto the grids of cer'd tain of said tubes and being connected said filament circuit at a point thereon of predeterminedpotential and meansin sai-d` coruluctorscomprisingresistancesl of the lila-y ments alone to cause a drop in the volwiage'` applied thereto from said lilarnent circuit. 2; A plurality o'l sets oli' electron tubves,` filament `battery, circuits associated Witlr said battery and connecting the filaments ol cach of said sets of' tubes in series, conductors leading to the: grids of certainyof the tubes of each set and being connectedto said lila-` ment circuits at points thereon of' prede tors leading to the'grids of certain `of the tubes oteach set and being connected to said filament circuits at points thereon! of pre determined potential, a grid battery, and means for associating said grid battery with j tubes of' each set and being connected to said filament circuits at points thereon of' predetermined potential, a grid battery, means for associating said gridi battery with said con ductors so as to cause a drop in the voltage applied thereto. from. said filament circuits, and an alternating current `path to ground associated with said grid battery'.

5.4 A! plurality ofi sets of electrontubcs, a filament battery, circuits associated with. lsaid battery and connecting the filamentsof each of said sets of' tubes in series,A a-conductor connected tol eacho't said filament circuitsy at points thereon of the same predetermined potential, a. pair of relatively high resistance elements included in said i coi-rdu'ctor,I conductors leading to the grids of certain of the tubes of eaclfr set andlbeing connected to said llast mentioned conductor ,at a point between said resistance elements,

and means in said conductors to cause a drop in the voltage applied thereto from said last mentioned connecting point.

\ In testimony whereof, I'have signed my namel to this specification this 15th day of May 1923.

SAMUEL P. sHAoKLEToN. 

